A 10-watt electrostatically-focused traveling-wave tube for satellite telemetry

Satellite environments impose several special requirements on microwave telemetry transmitting tubes, such as long life, high efficiency, and light weight. A microwave amplifier will be described which is designed to meet the following requirements: 10 watts power output, life greater than 10,000 hours, efficiency greater than 30%, weight less than 1.0 pound, and rugged construction to meet shock and vibration requirements. The basic tube is a forward-wave S-band traveling-wave tube amplifier which accomplishes electron-beam focusing by electrostatic means. The tube exhibits greater than 30 db gain so that it requires only a few milliwatts of r-f input to drive it to saturation power output. To achieve high efficiency, the electron beam is collected at a beam potential below that of the average helix potential. Whn the tube is used as an oscillator, feedback is accomplished by passing a fraction of the power output through a tuned cavity to drive the input, thus achieving high frequency stability. By adjusting the loaded Q of the cavity, the tube can be made electrically tunable over a range of ± 10 mcs by varying the cathode-helix voltage.